The UCSF Microbial Pathogenesis and Host Defense (MPHD) program provides a comprehensive, world-class training plan to prepare graduate students and postdoctoral fellows for future careers in academics, industry, public health, or teaching. The MPHD program's primary goal is to train the next generation of leaders in this critically important field. Recent rapid advances in microbial pathogenesis, immunology, the genetics, genomics, and systems biology provide unprecedented opportunities to improve the health of mankind worldwide. The importance of training our next generation of scientific leaders to use these tools for innovative approaches has never been greater. Our program provides outstanding trainees with funded research opportunities in cutting edge, interdisciplinary scientific training environments. UCSF hosts an unusual number of world-class laboratories in each aspect of microbial pathogenesis, including bacterial, viral, fungal, parasitic, and innate immunity research programs. The faculty has an outstanding track record of creative and high profile research, excellent mentoring, and substantial research funding, and thus attracts outstanding trainees. Likewise, the MPHD program has catalyzed new scientific directions and broadened the training opportunities in microbial pathogenesis by bringing together laboratories with traditional expertise in the field with those from diverse scientific fields. Thus, a major objective of our research training program is to capitalize on the strengths of the UCSF research community to create an integrative program focused on issues in host-microbe interactions. As an interdepartmental and intercampus program at UCSF, the MPHD Program is open to all UCSF graduate students and postdoctoral fellows with an interest in microbial pathogenesis. The program integrates students, postdoctoral fellows, and faculty from diverse programs, expertise, and backgrounds by nourishing synergistic interactions and facilitating new approaches not otherwise possible. MPHD trainees are drawn from an elite pool of very highly qualified students and postdoctoral fellows. Outstanding institutional core facilities are availabl to accelerate application of new and emerging technologies. The strong tradition of openness and collaboration among UCSF laboratories and research groups allows trainees to easily access diverse expertise from multiple faculty. The program is comprised of the following program-specific components: a weekly seminar series, a yearly Bay Area-wide symposium, yearly graduate student elective courses in MPHD, and a postdoctoral mentoring program that augments the already high caliber of postdoctoral training by matching fellows with an additional mentor separate from their PI (the affiliated graduate students are already cross-mentored through their respective graduate programs). In this grant renewal, we request continuation of 4 pre-doctoral slots and 2 post-doctoral slots, to provide support at the same level as in prior years. This support will allow us to continue our history of training the next generation of leader in microbial pathogenesis who will work to reduce the worldwide burden of infectious disease.